Better ditches help environment
CONWAY — Public officials in Conway and Horry County know it takes brains as well as brawn to prevent the city from flooding. Ditch-digging that once was a product of strong backs, picks and shovels now involves Ph.D.s, computers and digital mapping.
Leaders working with Clemson University’s Belle W. Baruch Institute of Coastal Ecology and Forest Science; Coastal Carolina University; and federal, state, local and volunteer groups, have restored two sections of the city’s main drain for storm water.
As a result, Crabtree Canal, once a silt-filled, debris laden, dead-water drainage ditch, is on its way to becoming a model modern ditch to manage the rainwater runoff from roads and roofs in an environmentally sustainable way. Today, after much digging and hauling to rebuild the canal, fish and plants thrive.
The second section restoration was completed late last year, when South Carolinians still were talking about drought. Then the rains came this year. Crabtree Canal handled runoff nearly every week this summer. Drainage ditches were built first to handle water flooding from croplands. As towns and cities developed, they spread out, adding more rooftops and parking lots for the rain to run off and spill into streets and sewers.
Clemson hydrologist Anand Jayakaran, stationed at Baruch, researches both natural and developed watersheds. He has been part of the team since 2007 when the partnership began that monitors the Crabtree Canal improvements. A stormwater specialist, Jayakaran works with developers, state and county agencies, homeowners and municipal officials to develop ways to reduce runoff.
“I study watersheds and how they are affected by rapid development along the coast,” Jayakaran said. “I look at how urban development affects the quantity of runoff from storm events and study ways to mitigate that runoff.”
Clemson scientists at the Baruch Institute focus on the environmental impact of changing land-use patterns, coastal natural resource conservation, forestry, water quality and watershed management. Research areas include biochemistry, ecosystems, hydrology and data visualization.
On a rare dry day, Jayakaran, county watershed planner Dave Fuss and Crabtree elected watershed directors George Jenkins Jr. and son, Hunter, toured the improvements. The Jenkinses are the second and third generations to be involved with flood control. In June 1964, it rained more than 10.3 inches in 14 hours, cutting Conway off from the surrounding area. George Jenkins Sr. helped convince the U.S. Army Corps of Engineers to build the canal a year later.
Jenkins Jr. and his son stooped to pick up trash as the tour ambled along the canal bank of the restored section that flows under U.S. and continues on, behind the Refuel gas station, into the mixed-hardwood Crabtree swamp, part of the Kingston Lake watershed. The swamp drains into the Waccamaw River, which flows to Winyah Bay in northeastern South Carolina.
“We learned a lot about what it takes to plan, build and maintain a project like this,” said the elder Jenkins. “A big lesson was to ‘let nature run its course’ and have the canal work like a stream flowing through a swamp. And it took commitment and coordination from many people and groups to get the project done. Susan Libes at Coastal Carolina and Dave Fuss from Horry have been involved from the beginning. So were Will Connor and Jack Whetstone from Clemson, and now Ani (Jayakaran).”
The Crabtree project reshaped the ditch and restored the surrounding area to be a flood plain, relying on native plants and grasses to slow the flow and filter stormwater. Dug by the U.S. Army Corps of Engineers in the 1960s, the ditch was a classic trapezoid: a U-shaped channel with a flat bottom. Thousands of ditches throughout the world look much the same, but research has shown there is better design: the two-stage channel.
“When I was in graduate school at Ohio State University, we studied farm ditches,” Jayakaran said. “We saw that U-shaped ones collapsed as the water eroded the banks, filling the channel with sediment that had to be removed. Natural streams work differently, carving a channel and building a flat ‘bench’ that acts like a mini-floodplain in the lower part of the ditch. The two-stage design adds stability and encourages vegetation to grow in the channel.
“The design works in urban areas like Conway, too. I think other communities ought to take look at what was done here. It’s way to manage the water, deal with changing conditions and meet environmental regulations.”
Jayakaran will use aerial mapping, flow measurements, flow models and other monitoring tools to collect information about how Crabtree Canal is performing. As coastal conditions change, affected by rising numbers of people who want to live near the ocean and by weather patterns that produce more rain, college-educated “ditch-diggers” are likely to stay busy.